This invention relates to finite amplitude sonar systems, and more particularly, to a sonic direction finding system wherein a beam of relatively high amplitude sonic energy is projected in a direction away from a source of sound for determining the direction of the source and characteristics of the sound radiated therefrom.
The detection of underwater sound and the determination of the direction of such a source of sound is accomplished by use of an array of sonic radiating elements which is many times longer than a wavelength of the sound to be measured in order that the array of sonic radiating elements produce a sufficiently narrow directivity pattern to permit a precise measurement of the direction of the source. A problem arises in the case of sources radiating sound at very low frequencies such as, for example, 50 Hz, since the relatively long wavelength of such sound necessitates a receiving sonar array of a prohibitively large size, too large for mounting on many vessels.